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Neuromorphic computing processes data faster and with less energy than electronics. Here, authors demonstrate a reconfigurable photonic reservoir computer that performs multiple machine learning tasks in parallel at ultrafast rates while using extremely low energy per operation.

Faraday isolators prevent back reflection of light through photonic systems, and are widespread at optical frequencies. Shalaby et al. show that the permanent magnet SrFe₁₂O₁₉can be used to generate a broadband rotation with low dispersion, and build an isolator suitable for short terahertz pulses.

Waveguides that can provide complex signal-processing functionalities while guiding terahertz signals are desired. Here, the authors report the independent processing of multiplexed signals by engineering the metal surface of a four-wire waveguide.

Here the authors show that the dipole-active phonon resonance of semiconducting nanocrystals can be hybridized by a strongly concentrated terahertz vacuum field of a plasmonic nanocavity, thus achieving strong plasmon–phonon coupling even in the absence of direct terahertz illumination.

The use of time-bin entangled qudits is hindered by the phase instability, timing inaccuracy and low scalability of current interferometric schemes. Here, the authors show a fiber-pigtailed photonic chip for generating and processing picosecond-spaced time-bin entangled qudits and utilize the system to implement a quantum key distribution protocol.

A scalable quantum processor based on the discrete-time quantum walk of time-bin-entangled photon pairs on synthetic temporal photonic lattices is realized on a fibre-coupled loop system. Key fundamental quantum operations are demonstrated.

The authors demonstrate a single-shot ultrafast terahertz (THz) photography system that can provide both the 2D spatial and 1D temporal imaging capabilities of ultrashort transient scenes with sub-picosecond temporal resolutions by engineering the electro-optic detection system.

On-chip nonlinear optics devices find a number of applications in modern optics from spectroscopy to communications. Here, the authors increase the degrees of freedom for frequency mixing by demonstrating the nonlinear interaction of perpendicularly-polarized modes in an integrated microring resonator.

Hyper-transport — an increase in diffusion beyond the ballistic-transport regime — is observed in an optical system.

Typically, Boolean logic gates have to compromise between high speed and low energy consumption which can become limiting at scale. Here, the authors demonstrate architectures for NOT and XNOR gates that enable simultaneous low power and fast operation.

Complex-valued neural networks can recognize phase-sensitive data in wave-related phenomena. Here, authors report a complex-valued optical convolution accelerator operating at over 2 TOPS for recognition of radar images, represents advances towards real-time analysis of complex satellite data.

The mathematical concept of parity'time symmetry, which was first introduced in field theories of quantum mechanics, has been demonstrated experimentally in a large-scale optical system. See Article p.167

Topological protection in disclination lattices that relies on non-trivial winding in momentum space and real space is used to confine and guide vortices that feature arbitrary high-order charges. This approach could help in the development of orbital angular momentum-based photonic devices.

A passively mode-locked laser system featuring cavity filtering and cavity-enhanced nonlinear interactions within an integrated microring resonator produces nanosecond optical pulses with a spectral width of 104.9 MHz.

Microphotonic frequency combs are chip-based light sources, until now confined to optics laboratories. Improved stabilities usher these devices out of the lab and into high-resolution astronomic spectrometer systems.

Based on CMOS-compatible spectral phase interferometry for direct electric-field reconstruction (SPIDER), researchers show that they are able to characterize both the amplitude and phase of ultrafast optical pulses with a time–bandwidth product of more than 100.

Controlling complex properties of optical systems, like the output of nonlinear light sources, is increasingly important for applications. Here, Wetzel et al. use an actively-controlled photonic chip to prepare patterns of femtosecond laser pulses used for tailoring supercontinuum generation.

Authors present a fibre Bragg grating-based all-pass spectral phase filter with an unprecedented frequency resolution of 1 GHz, at least 10× improvement compared to a standard optical waveshaper. Using the all-fibre phase filter, fully passive NOT and XNOR logic operations are experimentally demonstrated at ultrafast speeds with few-fJ/bit energy consumption.

Slow nonlinearities of a free-running microresonator-filtered fibre laser are shown to transform temporal cavity solitons into the system’s dominant attractor, leading to reliable self-starting oscillation of microcavity-solitons that are naturally robust to perturbations.

Some topological boundary states are symmetry protected. Experiments with photonic lattices now show that the protection via sub-symmetry is enough to ensure topological modes, even if the full symmetry and topological invariant are destroyed.

Low amplitude noise on an otherwise constant-intensity wave can grow exponentially and induce nonlinear dynamical behaviour. Here, the authors present time-domain measurements of a phenomenon arising from such modulation instability: the emergence of highly localised breathers in an optical fibre.

An optical vector convolutional accelerator operating at more than ten trillion operations per second is used to create an optical convolutional neural network that can successfully recognize handwritten digit images with 88 per cent accuracy.

Microcombs provide many opportunities for integration in optical communications systems. Here, the authors implement a soliton crystal microcomb as a tool to demonstrate more than 44 Tb/s communications with high spectral efficiency.

The creation and manipulation of large quantum states is necessary for quantum information processing tasks. Three-level, four-partite cluster states have now been created in the time and frequency domain of two photons on-chip.

The on-chip generation of high-dimensional frequency-entangled states and their spectral-domain manipulation are demonstrated, introducing a powerful and practical platform for quantum information processing.

Generating stable frequency combs with desired features is crucial for enabling applications in diverse fields, such as telecommunications, spectroscopy, and artificial intelligence. In this work, the authors demonstrated an autonomous optimization scheme based on genetic algorithms to tailor coherent microcombs produced by a microring resonator.

This Review summarizes the recent progress in ultrahigh-bandwidth optical-fibre communications based on integrated optical frequency comb technologies, or integrated Kerr microcombs, highlighting the challenges and opportunities ahead.

This Review describes quantum frequency combs that operate via photon entanglement, beginning with mode-locked quantum frequency combs followed by energy–time entanglement methods. The use of photonic integration and fibre-optic telecommunications components in enabling the quantum state control are also discussed.

By nesting a Kerr microresonator in a fibre loop with gain, 50-nm-wide bright microcavity-based soliton combs with a mode efficiency of 75% can be induced at average powers more than one order of magnitude lower than the Lugiato–Lefever soliton power threshold, facilitating real-world applications.

Signal processing is key to communications and video image processing for astronomy, medical diagnosis, autonomous driving, big data and AI. Menxi Tan and colleagues report a photonic processor operating at 17Tb/s for ultrafast robotic vision and machine learning.

Cavity-solitons in microresonator-filtered fibre lasers are robust states with self-recovery capabilities that emerge when a delicate balance of energy-dependent nonlinearities is achieved. In this work, the authors make use of the dispersive Fourier transform to understand the dynamics leading to a soliton bonded with a quasi-continuous wave.

This article reviews recent progress in the use of silicon nitride and Hydex as non-silicon-based CMOS-compatible platforms for nonlinear optics. New capabilities such as on-chip optical frequency comb generation, ultrafast optical pulse generation and measurement using these materials, and their potential future impact and challenges are covered.